Measles Outbreak ---- Netherlands, April 1999--January 2000

On June 21, 1999, a cluster of five cases of measles was reported among the
390 students attending a religion-affiliated elementary school in the Netherlands.
Persons belonging to this religious denomination routinely do not accept vaccination.
Municipal health services (MHSs) investigated and found 160 suspected measles
cases among children attending the school. By February 4, 2000, 2961 measles cases,
includ
ing three measles-related deaths, had been reported by 35 MHSs to the national
registry. This report summarizes the investigation of the measles outbreak in the
Netherlands, which indicated that measles can be a severe disease among unvaccinated
populations in the Netherlands.

Measles is a notifiable disease in the Netherlands, and cases that occurred during
this outbreak were reported by physicians to the local MHS as part of routine
surveillance. The vaccination status of ill persons was reviewed based on written records kept
by reporting physicians and sent to the vaccination registry. In April 1999, the first cluster
of measles cases occurred, followed by the reported elementary school outbreak in
June. No cases of measles with onset in May were reported, and transmission was low
during June and July (Figure 1). When schools reopened in August, the number of cases
increased. The outbreak peaked during October--November, then decreased rapidly. As
of February 4, the last reported cases had onset during the week of January 16. Since
then, the number of reported cases has decreased substantially, suggesting that the
outbreak is ending.

From April 15, 1999, to February 4, 2000, 2961 cases of measles were reported in
35 (67%) of the country's 52 MHSs; 2317 (78%) were reported by 10 MHSs. All
reporting municipalities have large communities affiliated with the religious group. Of the
105 case-patients tested for measles immunoglobulin type M, 100 (95%) had
serologically confirmed measles.

Complications among acute measles case-patients were assessed by telephone
follow-up with reporting physicians; 510 (17%) cases had one or more
complications and/or hospitalizations (Table 1). Three patients died as the result of measles
complications: one child aged 2 years had an underlying cardiac disorder and subsequent
cardiac failure, one child aged 3 years developed myocarditis, and one adolescent aged 17
years developed kidney failure and acute respiratory distress syndrome. Sixty-eight
(2.2%) persons were reported hospitalized: 37 (1.2%) for pneumonia, seven (0.2%) for
dehydration, five (0.2%) for encephalitis, four (0.1%) for high fever, three (0.1%) for shortness
of breath, two (0.1%) for severe otitis media, two (0.1%) for croup, and six (0.2%) for
other reasons. Two persons developed measles while hospitalized for other reasons.

Of the 2882 patients whose ages were known, the median age was 6 years (range:
0--52 years): 95 (3%) were aged <1 year; 949 (33%), aged 1--4 years; 1282 (44%), aged
5--9 years; 382 (13%), aged 10--14 years; 87 (3%), aged 15--19 years; and 87 (3%), aged
>20 years. Information on vaccination status was available for 2907 persons; 2770 (95%)
were unvaccinated and 137 (5%) were vaccinated children. Of the 137, 117 (85%) were aged
<9 years and all had received one dose of measles, mumps, and rubella vaccine (MMR);
in 20 (15%) children the number of doses was unknown. Based on data from the
national registry, 2749 persons whose ages were known were unvaccinated: 2317 (84%)
persons eligible for vaccination were not vaccinated for religious reasons and 173 (6%) for
other reasons (e.g., lack of concern about measles or concern about adverse events); 187
(7%) were not eligible for vaccination: 160 (85%) were aged <14 months (the
recommended age for administration of the first dose of measles vaccine), 20 (11%) were born
before 1976 (the year measles vaccination was introduced), and seven (4%) had a
contraindication for measles vaccination. For the remaining 72 (3%) unvaccinated persons, the
reason for not being vaccinated was unknown.

In response to the outbreak in the Netherlands, on July 1, control activities
were implemented, including 1) tracing contacts of cases, 2) offering vaccine or
immunoglobu
lin to susceptible contacts, 3) alerting all secondary-care and tertiary-care hospitals
about the measles outbreak, 4) requesting general physicians to report all suspected cases,
5) conducting catch-up vaccination sessions at MHSs and mother and child clinics, 6)
increasing media attention about undervaccination, and 7) urging parents to
complete vaccination of children.

Editorial Note: The three measles-related deaths and 68 hospitalizations that
occurred among 2961 cases in the Netherlands indicate that measles can be severe and
may result in death even in industrialized countries. Rates of complications reported in
this outbreak are comparable with those in the United States and other industrialized
countries (1).

Measles notification and vaccination began in 1976 in the Netherlands, where
measles epidemics have occurred every 5--7 years: 1976, 1983, 1988, 1992--1993, and
1999--2000. Since 1987, two doses of MMR have been recommended at age 14 months and
9 years. Measles vaccination is not mandatory for entry into school in the
Netherlands. During 1997--1999, nationwide coverage of children for both doses was reported
between 95% and 96% (2). However, coverage was not distributed uniformly
throughout the country. In 1999, coverage ranged from 53% to 90% in municipalities that had a
high percentage of residents who were members of a particular group that refrains
from vaccination on religious grounds (2). This community in the Netherlands, estimated
at 300,000 persons (2% of the overall population) lives as a close social network in a
circumscribed geographic area mostly in the provinces of Gelderland, Utrecht,
Zuid-Holland, and Zeeland. Approximately half of the 4%--5% of unvaccinated persons in the
Netherlands are members of this group. Although the Netherlands has high overall MMR
coverage, 36 (7%) of 539 municipalities have one-dose coverage of <90%.

Although measles is more severe in malnourished or immunosuppressed
persons, severe disease or death may result in persons with no underlying illness. Measles
vaccine is a highly effective method for preventing this disease, and lack of
vaccination resulted in this outbreak. Similar to the outbreak of poliomyelitis among religious
communities in 1992 (3,4), measles spread from the Netherlands to Canada through
visiting relatives. The resulting outbreak in Canada was limited to 17 cases within the
religious community possibly because stringent control measures were taken
(5).

Until measles is eradicated worldwide, epidemics will continue to occur
periodically in the Netherlands. The World Health Organization (WHO) has established goals to
eliminate measles as an indigenous disease from the Region of the Americas by the end
of 2000, the European Region by 2007, and the Eastern Mediterranean Region by 2010.
To reach these goals, the WHO regional office for Europe has conducted workshops
aimed at assisting participating countries to develop an elimination strategy based on the
percentage of persons susceptible to measles in their population. In addition to these
activities, increased commitment at the regional and national levels is needed to
eliminate measles in the European Region (6).

References

CDC. Measles, mumps, and rubella----vaccine use and strategies for elimination of
measles, rubella, and congenital rubella syndrome and control of mumps: recommendations of
the Advisory Committee on Immunization Practices (ACIP). MMWR 1998:47(no. RR-8).

Ramsey M, Expanded Programme on Immunization in the European Region of the World
Health Organization. Measles: a strategic framework for the elimination of measles in the
European Region, February 1997. Copenhagen, Denmark: World Health Organization, 1999.

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